1. Field of the Invention
The present invention generally relates to an actuator including an electro-mechanical transducer film, a method of manufacturing the actuator, and a liquid droplet ejecting head, a liquid droplet ejecting apparatus, and an image forming apparatus having the actuator.
2. Description of the Related Art
An “electro-mechanical transducer element” including an electro-mechanical transducer film sandwiched between electrodes has been used in an inkjet recording apparatus as an image forming apparatus, etc. in related technologies. Due to various advantages such as very low sound (noise), fast print speed, higher ink flexibility, and capability of using a plain sheet, such an inkjet recording apparatus has been widely used as an image recording apparatus or an image forming apparatus such as a printer, a facsimile machine, a copier, etc.
A liquid droplet ejecting head used in the inkjet recording apparatus mainly includes nozzles ejecting ink droplets, a liquid chamber (a.k.a. e.g., an ejecting chamber, a pressurizing chamber, a pressure chamber, or an ink flow path) which is in communication with the nozzles, and a pressure generation means which generates a pressure in the liquid chamber. As such a pressure generation means, there has been known a piezo-type pressure generation means which ejects liquid droplets by deforming and displacing a vibration plate that is formed, as a part of a wall surface of the liquid chamber, by using an electro-mechanical transducer element such as a piezoelectric element.
The electro-mechanical transducer element used in the piezo-type pressure generation means includes a lower electrode (a first electrode), an electro-mechanical transducer layer, and an upper electrode (a second electrode), which are laminated to each other. In a case of a liquid droplet ejecting head including a plurality of the liquid chambers, the electro-mechanical transducer elements corresponding to the respective liquid chambers are disposed (provided).
As the electro-mechanical transducer layer of the electro-mechanical transducer element, lead zirconate titanate (PZT) ceramics or the like may be used. Such objects may generally be called a “metal composite oxide” due to the multiple metal oxides included as the main components.
Here, as a method of forming the electro-mechanical transducer film, there has been known a method of ejecting liquid droplets in which liquid droplets of an application liquid including a material for forming the electro-mechanical transducer film are ejected from nozzles so that the application liquid is applied onto a predetermined part on an electrode (see, for example, Japanese Laid-open Patent Publication Nos. 2003-297825 and 2006-176385).
Further, Japanese Laid-open Patent Publication No. 2011-146601 discloses a method of forming the electro-mechanical transducer film based on a sol-gel method in which two steps are repeated so as to obtain a desired film thickness, the two steps including a step of partially applying a sol-gel liquid, by an inkjet method, onto an electrode whose surface is partially modified and a step of sol-gel liquid drying, thermally decomposing, and crystallizing the partially applied sol-gel liquid.
Further, as for the liquid droplet ejecting head, there have been various proposals about the sizes of the liquid chamber and the electro-mechanical transducer element formed on the substrates included in an actuator.
For example, Japanese Laid-open Patent Publication No. 2002-370353 discloses the structure having the following sizes of a liquid injection head which includes nozzles ejecting ink droplets, a liquid chamber formed on a substrates and in communication with the nozzles, a vibration plate formed as a part of a wall surface of the liquid chamber, and a piezoelectric element (electro-mechanical transducer element).
Specifically, a relationship Lu≦Lp<Ll is satisfied where the symbols “Lu”, “Lp”, “Ll”, and “L” denote the lengths in a chamber arranging direction of the upper electrode, the piezoelectric film, the symbol, the lower electrode, and the liquid chamber, respectively. By forming so as to satisfy the above relationship, it becomes possible to remove the problem regarding the manufacturing process, reduce the leak current between the upper and lower electrodes, reduce the sizes, and obtain higher density.
Further, another relationship Lu<L is also satisfied. By doing this, it becomes possible to effectively deform the vibration plate and effectively inject liquid.